Thermal stabilization of tellurium in mineral acids solutions: Use of permanent modifiers for its determination in sulfur by GFAAS

Talanta ◽  
2006 ◽  
Vol 69 (1) ◽  
pp. 199-203 ◽  
Author(s):  
Juana Pedro ◽  
Jorge Stripekis ◽  
Adrián Bonivardi ◽  
Mabel Tudino
Keyword(s):  
Thermal Stabilization ◽  
Mineral Acids ◽  
Permanent Modifiers

NICROFER 3033

Alloy Digest ◽  
2004 ◽  
Vol 53 (2) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Heat Treating ◽  
High Chromium ◽  
Temperature Performance ◽  
Mineral Acids ◽  
Mixed Acids

Abstract Nicrofer 3033 is a high-chromium austenitic material for service in hot mineral acids and mixed acids. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-508. Producer or source: VDM Technologies Corporation. Originally published April 1996, revised February 2004. See also Alloy Digest SS-687, July 1997.

Temporal Patterns of Acidification of Rivers in Nova Scotia and Newfoundland and their Relationship to Sulphate Emissions

1988 ◽  
Vol 23 (4) ◽  
pp. 532-541
Author(s):  
G. D. Howell ◽  
P.E.J. Green ◽  
C.A. Field ◽  
B. Freedman
Keyword(s):  
Statistical Analysis ◽  
Nova Scotia ◽  
Water Chemistry ◽  
Sulphur Dioxide ◽  
Low Ph ◽  
Hydrogen Ion ◽  
Atlantic Canada ◽  
Atmospheric Loading ◽  
Mineral Acids ◽  
Sulphur Dioxide Emission

Abstract Twenty-eight rivers in Atlantic Canada are sampled monthly, and have periods of record dating back as far as 1965. Statistical analysis of water chemistry for rivers in areas of Nova Scotia and Newfoundland that are believed to be sensitive to acidification has revealed that pH was significantly lower during the late 1960’s and early 1970’s. Annual hydrogen ion export for selected rivers was also greater during this period. This period of relatively low pH and large hydrogen ion export corresponds to a peak of North American sulphur dioxide emission, suggesting that these rivers may be responding to atmospheric loading of anthropogenic mineral acids.

Extraction of hafnium(IV) with organophosphorus reagents from solutions of mineral acids mixtures

1979 ◽  
Vol 44 (12) ◽  
pp. 3656-3664
Author(s):  
Oldřich Navrátil ◽  
Jiří Smola ◽  
Rostislav Kolouch
Keyword(s):  
Ionic Strength ◽  
Aqueous Phase ◽  
Organic Phase ◽  
Perchloric Acid ◽  
Synergic Effect ◽  
Salting Out ◽  
Initial Concentration ◽  
Mixed Complexes ◽  
Synergic Extraction ◽  
Mineral Acids

Extraction of hafnium(IV) was studied from solutions of mixtures of perchloric and nitric acids and of perchloric and hydrochloric acids for constant ionic strength, I = 2, 4, 6, or 8, and for cHf 4 . 10-4 mol l-1. The organic phase was constituted by solutions of some acidic or neutral organophosphorus reagents or of 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, or N-benzoyl-N-phenylhydroxylamine in benzene, chloroform, or n-octane. A pronounced synergic extraction of hafnium proceeds only on applying organophosphorus reagents from an aqueous phase whose acidity is not lower than 3M-(HClO4 + HNO3) or 5M-(HClO4 + HCl). The synergic effect was not affected markedly by a variation of the initial concentration of hafnium in the range 1 . 10-8 -4 .10-4 mol l-1, it lowered with increasing initial concentration of the organophosphorus reagent and decreasing concentration of the H+ ions. It is suggested that the hafnium passes into the organic phase in the form of mixed complexes, the salting-out effect of perchloric acid playing an appreciable part.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

Cyclohexylation of Naphthalene Over USY Zeolites

1999 ◽  
Vol 64 (1) ◽  
pp. 138-148 ◽  
Author(s):  
Miroslav Michvocík ◽  
Dušan Mravec ◽  
Milan Hronec ◽  
Agáta Smiešková ◽  
Pavol Hudec
Keyword(s):  
Liquid Phase ◽  
Hydrochloric Acid ◽  
Thermal Stabilization ◽  
Y Zeolite ◽  
Zeolite Structure ◽  
Positive Effect

The influence of thermal stabilization of NH4-Y zeolite and modification of USY zeolites with solutions of hydrochloric acid on the cyclohexylation of naphthalene in the liquid phase was studied. Removal of the part of extra-framework aluminium from zeolite structure has a positive effect on both conversion of naphthalene and amount of dicyclohexylnaphthalenes formed. Modification of zeolites leads to an increase in conversion and selectivity of β-substitution in the naphthalene cyclohexylation.

Thermal stabilization of immobilized α-amylase by coupling with proline

1995 ◽  
Vol 30 (4) ◽  
pp. 299-303 ◽  
Author(s):  
Vasanthy Arasaratnam ◽  
Kandiah Balasubramaniam
Keyword(s):  
Thermal Stabilization
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